Air propeller



Aug. 7, 1934.

J. TOTH 1,968,918

RRRRRRRRRR ER iill/ll/ lllllillm/li/lim JOSEPH ToTH INVENT OR M 96 7ATTORNEYS Patented Aug. 7, 1934 UNITED STATES PATENT OFFICE Claims.

This invention relates to screw propellers of the kind in which the rearor suction faces of the blades are curved in known manner, and has forits object to provide a propeller, more par- 5 ticularly for use withaircraft, of equally good efllciency both during horizontal flying andwhen climbing.

The cross-section of the blade of an air propeller of the type usuallyemployed on airplanes generally possesses a well known shape with acontour line consisting of a curve and a straight line, respectively.The curve between the leading edge and the trailing edge is thedirectrix of the surface forming the suction side of the propeller bladewhilst the straight line is the directrix of the surface forming thepressure side of the propeller blade.

In air propellers it has been found to be a general rule, that if thestarting angle of the individual blades is increased or diminished, itis possible to ensure that the output of the engine is employed forincreasing the flying speed, for instance when flying at the same level,or of developing an increased tractive effort as, for example, whenascending.

I am aware that it is already known to form one side of a propellerblade with faces disposed in different transverse planes. For example,it has hitherto been known to construct a screw pro-- 10 peller forships in which the rear or suction side of each blade is formed by twofaces arranged at an angle to each other, that face adjacent the leadingedge being concave whilst that adJacent the trailing edge is flat. Inanother form of screw :5 propeller for ships hitherto suggested theforward or leading portion is slightly inclined inboard with relation tothe major portion of the blade.

Experiments made with air propellers have 0 led to the surprisingresult, that air propellers will develop an amount of performanceexceeding all expectations, and also ensure a degree of quietness ofrunning most favourable in view of increasing the life of the airplane,if, differently 5 from the types of design known and usual up to now,the prewur'e surface of the propeller blade is, as shown on theembodiment shown by way of example onFig. 1, made of two plane surfacesI and a, of which the surface I. the first 1 in order of sequence whenproceeding from the inlet edge to the outlet edge, forms with thedirection of rotation an angle ,8, which is larger than the angle 7formed with the said direction of rotation by the second surface a.

i Notably when, at the occasion of trial flights Hungary December 31,1930 a propeller A having a cross-section according to the inventiondimensioned for a certain output and number of revolutions per minutehas repeatedly been compared with an ordinary propeller B as shown indotted lines on Fig. 1 dimensioned for the same output and number ofrevolutions per minute, it was shown by reliable and accurateinstruments that with a propeller A having a cross-section according tothe present invention it is possible when flying at a level to 55 attaina higher flying speed and when ascending to realize a larger tractiveeffort per horse power, than can be realized with the ordinary type B ofpropeller of usual cross-section.

The comparative controlling experiments for 7 instance were carried outwith a Fokker C. V. D. type airplane, fitted with a W. M. Jupiter 420 H.P. engine, with the ordinary propeller of the airplane, and with thepropeller according to the present invention, immediately one after theother, in identical conditions, the two propellers being interchangedafter each flight.

The barograph measuring the rising of the airplane, as well as theinstruments measuring its speed, were ofliciaily attested instruments,the correct functioning of which was ascertained before, and after.

The controlling measurements showed the following, almost identicalresults:

86 Rising with full gas, at 120 km. wlmthdmal With the polspeed hour,and identical ler amon to was: revolutions opener the lnventfim o.Fromlwmtollwm. 9 Accordin tobarogra h 2'67"mp. 3'02" 2'23" W Ra-mlculiited to sea vel airmp mum r23" resp. 3W 2'40" tasp. 2'41 0. From a. toma 1a.

According to bamgra h OWresp. 7'03" 4'64" reap. 8W Ito-calculated to volairpremn'e 7'18" mp. 7'45 8'14" mp. W

starting angle of the part of the delivery surface which extends fromedge i to outlet edge b has been chosen so as to be smaller than thestarting angle of the propeller blade B. Now, it is known that byincreasing the starting angle while output and number of revolutions perminute remain unchanged it is possible to increase the flying speed,whilst, by diminishing the starting angle, it is possible to increasethe tractive effort per horse power.

In order to obtain the best possible performance from an airplane itwould be advisable to fit two propellers of different type on it, one ofwhich would serve for flying at the same level i. e. for attaining ashigh a flying speed as possible whilst the other propeller would beemployed for ascending, i. e. for attaining a tractive effort of asgreat magnitude as possible. The air propeller accord ing to theinvention may be considered as representing the combination of two suchdifferent types of air propellers i. e. as representing an air propellerhaving two inlet edges a, i and one outlet edge b, whilst at the sametime the starting angle of the first, for practical reasons, preferablynarrow, part I of the pressure surface of the air propelleris madelarger than that of the: second, preferably also narrow, part g of thepressure surface of the air propeller.

From the embodiment shown in Fig. 1 it also appears that in the case ofair propellers dimensioned for the same performance and number ofrevolutions per minute the frontal resistance of the propeller A-according to the invention, which resistance is proportional to thelength m, is lower than the frontal resistance of the ordinary type ofpropeller B, which is proportional to the length n.

Finally it should bementioned that the dividing line i between the twoparts f-and g of different angle of the delivery surface should, asshown on Fig. 2, be chosen so as to make the surface larger than thesurface g.

Having described my invention and set forth its'merits, what I claim anddesire to secure by Letters Patent is:-

1. Anairplane propeller for aircraft, having the pressure side of eachblade which extends {from the leading edge, formed at the intersectionof a cross-sectional plane transversely through the same with two planesrespectively disposed at an angle to each other, of which two planesthat adjacent to the leading edge is disposed at a greater angle to thedirection of rotation than that adjacent to the trailing edge, while thegreater portion of the suction side of the propeller from the trailingedge transversely inward is practically parallel with the plane of thepressure side adjacent to the leading edge.

2. An airplane propeller according to claim 1, wherein the relativetransverse widths of the two angular planes of the pressure side aredifferent and the point of intersection of the two planes is spaced fromthe leading edge-a sufficient distance to make the plane adjacent tosaid leading edge greater throughout its entire length than the planeadjacent to the trailing edge.

3. An airplane propeller according to claim 1, wherein the portion ofthe suction side of the propeller which is practically parallel with theplane of the pressure side adjacent to the leading edge, is graduallycurved smoothly downward toward the leading edge to present a fullcurve, so that in cross section the blade has a substantial thicknessand consequently great strength as well as superior aerodynamicproperties.

4. A; screw propeller for aircraft, having the 1 pressure side of eachblade which extends from the leading edge. formed at the intersection ofa cross-sectional plane transversely through the same with two planesrespectively disposed at an angle to each other, of which two planesthat 10 adjacent to the leading edge is disposed at a greater angle tothe direction of rotation than that adjacent to the trailing edge, whilethe point" of intersection of the two a ngular planes is spaced from theleading edge a sufficient distance to 11 make the plane adjacent to saidleading edge greater throughout its entire length than the planeadjacent to the trailing edge. 7

5. An airplane propeller according to claim 4,

wherein the intersection of the two angular planes 1] forms asubstantially straight line throughout its entire length and is disposedsubstantially at right angleswith the axis ofthe propeller shaft and ispractically parallel with and spaced rearwardly from the individuallongitudinal axis of 1:

the blade while the leading and trailing edges are curvedconvexly inopposite directions so-that said intersecting angular planes are bothwidest at their intermediate portions.

JOSEPH "ro'rH.

